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virtual_memory.hpp
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virtual_memory.hpp
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#pragma once
// STD
#include <map>
#include <memory>
#include <algorithm>
#include <type_traits>
// VM
#include "virtual_section.hpp"
namespace vm
{
class virtual_memory
{
public:
static constexpr const size_t page_size = 0x1000;
bool allocate(std::uint8_t* address, size_t size);
bool free(std::uint8_t* address);
private:
using section_pointer_t = std::_Ptr_base<vm::virtual_section>::element_type*;
template<typename T>
T handle_iterative_read(uint8_t* address, section_pointer_t section, const size_t& page_index)
{
T result{};
auto page_address = address;
auto current_page_index = page_index;
size_t buffer_offset = 0;
size_t bytes_left = sizeof(T);
do
{
const auto page_offset = vm::virtual_memory::get_page_offset(page_address);
const auto count_to_end = vm::virtual_memory::page_size - page_offset;
const auto bytes_read = std::min(page_offset == 0 ? vm::virtual_memory::page_size : count_to_end, bytes_left);
auto page_buffer = reinterpret_cast<std::uint8_t*>(section->get(current_page_index));
for (auto i = 0; i < bytes_read; i++)
{
auto buffer = reinterpret_cast<std::uint8_t*>(&result);
buffer[buffer_offset + i] = page_buffer[page_offset + i];
}
page_address = nullptr;
buffer_offset += bytes_read;
bytes_left -= bytes_read;
++current_page_index;
} while (bytes_left > 0);
return result;
}
template<typename T>
void handle_iterative_write(T& value, uint8_t* address, section_pointer_t section)
{
const auto buffer = reinterpret_cast<std::uint8_t*>(&value);
size_t buffer_offset = 0;
size_t bytes_left = sizeof(T);
auto current_page_index = vm::virtual_memory::get_page_index(address, section->base());
auto page_address = address;
do
{
const auto page_offset = vm::virtual_memory::get_page_offset(page_address);
const auto count_to_end = vm::virtual_memory::page_size - page_offset;
const auto bytes_written = std::min(page_offset == 0 ? vm::virtual_memory::page_size : count_to_end, bytes_left);
auto page_buffer = reinterpret_cast<std::uint8_t*>(section->get(current_page_index));
for (auto i = 0; i < bytes_written; i++)
{
page_buffer[page_offset + i] = buffer[buffer_offset + i];
}
page_address = nullptr;
buffer_offset += bytes_written;
bytes_left -= bytes_written;
++current_page_index;
} while (bytes_left > 0);
}
public:
template <typename T>
T read(std::uint8_t* address)
{
auto page_start = vm::virtual_memory::round_to_page(address);
const auto search = this->address_space().find(page_start);
if (search != this->address_space().end())
{
auto section = search->second.get();
const auto page_index = vm::virtual_memory::get_page_index(page_start, section->base());
const size_t buffer_size = sizeof(T);
const auto next_page_start = page_start + vm::virtual_memory::page_size;
const bool exceeds_page = (address + sizeof(T) ) >= next_page_start;
if (!exceeds_page)
{
const auto page_offset = vm::virtual_memory::get_page_offset(address);
return *reinterpret_cast<T*>(section->get(page_index) + page_offset);
}
else
{
return handle_iterative_read<T>(address, section, page_index);
}
}
throw std::exception("Pagefault");
}
template <typename T>
void write(T& value, std::uint8_t* address)
{
const auto page_start = vm::virtual_memory::round_to_page(address);
const auto search = this->address_space().find(page_start);
if (search != this->address_space().end())
{
auto section = search->second.get();
const auto next_page_start = page_start + vm::virtual_memory::page_size;
const bool exceeds_page = (address + sizeof(T)) >= next_page_start;
if (!exceeds_page)
{
const auto page_index = vm::virtual_memory::get_page_index(address, section->base());
const auto page_offset = vm::virtual_memory::get_page_offset(address);
*reinterpret_cast<T*>(section->get(page_index) + page_offset) = value;
}
else
{
handle_iterative_write(value, address, section);
}
return;
}
throw std::exception("Pagefault");
return;
}
using memory_map_t = std::map<std::uint8_t*, std::shared_ptr<vm::virtual_section>>;
memory_map_t& address_space();
private:
template <typename T>
static constexpr T round_to_page(T address)
{
return reinterpret_cast<T>(reinterpret_cast<std::uint64_t>(address) & ~(0xFFF));
}
template <typename T>
static constexpr std::uintptr_t get_page_offset(T address)
{
return reinterpret_cast<std::uintptr_t>(address) & (0xFFF);
}
template <typename T>
static constexpr size_t get_page_index(T address, T base_address)
{
const auto page_delta = vm::virtual_memory::round_to_page(address) - vm::virtual_memory::round_to_page(base_address);
return page_delta / vm::virtual_memory::page_size;
}
memory_map_t m_address_space;
};
}